THE EVALUATION of dirt costs on diesel-electric locomotives made in this paper is admittedly extremely approximate in nature because of the scarcity of factual data and the many assumptions used in lieu thereof. It divides the locomotive into three main categories: the diesel engine (with cost figures of fair accuracy), and electric apparatus and other apparatus with dirt costs of Â¿order-of-magnitudeÂ¿ approximations only. Dirt costs are estimated on a total national basis, divided between cleaning and repair costs, with further subdivision as avoidable or nonavoidable.